A conventional drawer slide assembly 10 is shown in FIGS. 1 and 2 and comprises an inner slide member 11 affixed to the wall of drawer (not shown), an outer slide member 13 affixed to the wall of cabinet (not shown), and a ball bearing retainer 12 provided between the inner slide member 11 and the outer slide member 13. The ball bearing retainer 12 comprises two rows of ball bearings 121 in which each row rolls against opposite grooves along either one of two lengthwise edge portions of the inner slide member 11 and the outer slide member 13. The provision of ball bearings 121 can reduce friction when the inner slide member 11 slides with respect to the outer slide member 13, i.e., facilitating retracting or extending operation of the drawer. However, the prior art suffered from several disadvantages. For example, the drawer tends to slide out of the cabinet when the cabinet is disposed in an inclined supporting surface. This is because there is no provision of a device in the slid assembly 10 for locking the retracted drawer.
Another conventional drawer slide assembly 20 for overcoming the above problem is shown in FIG. 3 and comprises an elongated groove-shaped outer slide member 21, and an inner slide member 22 slidably received in the groove of the outer slide member 21 by means of a ball bearing retainer 23 having two rows of ball bearings each rolling either between a top wall of the inner slide member 22 and an upper inner groove of an inner section 211 or between a bottom wall of the inner slide member 22 and a lower inner groove of the inner section 211. A large space 213 is formed between the inner slide member 22 and an outer section 212 so as to mount a device for locking retracted drawer slide 24 in a rear portion of the space 213.
The device for locking retracted drawer slide 24, as illustrated in FIGS. 4 and 5, is affixed to a seat 241 on an inner surface of the inner section 211 by means of a spring 242. The spring 242 has one end secured to the seat 241 and the other end secured to a hook 2431 of a sliding member 243. The sliding member 243 further comprises a pin 2432 slidable along an elongate L-shaped groove 2411 on the seat 241, and a notch 2433 adapted to receive a lock pin 221 on the inner slide member 22. In an extending operation of drawer, the sliding member 243 moves by sliding the inner slide member 22 forwardly in response to receiving the lock pin 221 in the notch 2433. The pin 2432 will change its moving direction after reaching a turning point of the L-shaped groove 2411, i.e., the sliding member 243 turns. Thereafter, the lock pin 221 disengages from the notch 2433 for permitting a further movement of the inner slide member 22. In a retracting operation of the drawer, slide the inner slide member 22 inwardly until the lock pin 221 enters the notch 2433 and is retained therein. And in turn, the sliding member 243 turns to move the pin 2432 to pass the turning point. Once the pin 2432 passes the turning point, the sliding member 243 and thus the inner slide member 22 automatically move inwardly along the groove 2411 due to the compression of the spring 242. The second prior art is able to position the retracted drawer. But this is still unsatisfactory for the purpose for which the invention is concerned for the following reasons: The second prior assembly is relatively complex in constructions, relatively large, costly to manufacture, trouble-prone, and unreliable in use and thus has not found wide acceptance. Thus, the need for improvement still exists.